The head of China's National Bureau of Statistics (NBS) said that contrary to reports, China has not overtaken the U.S. as the world's largest economy, reports China state news agency Xinhua.

A 2014 study by the International Comparison Program (ICP) projected that China would overtake the U.S. last year based on purchasing power parity (PPP). PPP measures gross domestic product (GDP) in terms of prices of the same goods between nations.

"The NBS does not countenance these claims by some scholars and media organizations," said bureau head Ma Jiantang at a press conference in Beijing. "For various reasons, we think the PPP methodology might have underestimated actual price levels in China, and over-estimated China's GDP. With that proviso, we don't agree with the results."

PPP takes into account the purchasing power of a currency rather than market exchange rates. For example, it determines how many cars, McDonald's Big Mac's, units of electricity or university educations can one person's salary buy in one nation, as opposed to another person's salary in a different country.

Xinhua points out that despite a growing economy, China is still a developing country with a massive population of 1.3 billion, which means per capita GDP is still very low.

Latest data released by the NBS showed the Chinese economy expanded 7.4 percent year on year to 63.65 trillion yuan ($10.4 trillion) in 2014.